1. Field
The disclosure relates to electronic circuit design, and in particular, to the design of biasing circuits for class AB amplifiers.
2. Background
In the art of electronic amplifier design, class AB amplifiers are commonly used to deliver large currents to a load, with low distortion. A class AB amplifier stage is biased such that the current consumption in the absence of an input signal (i.e., the “quiescent” current) is a small fraction of the peak current that is delivered to the load. For instance, in a typical class AB amplifier for audio applications, the quiescent current may be as low as 0.2% of the peak current. The quiescent current is an important parameter since it affects the overall power consumption of a device incorporating the amplifier.
While a class AB amplifier may be biased to have low quiescent current under nominal conditions, the quiescent current may vary greatly when parameters like process, temperature, or the supply voltage deviate from their nominal values. It would be desirable to provide a biasing scheme for class AB amplifiers that is robust to changes in the above-mentioned parameters, thereby maintaining good power efficiency and linearity for the amplifier across a wide range of operating conditions.